In many branches of industry, labels or identification plates are needed for the marking of products. Examples are the producers of textiles and the producers of electrical/electronic apparatus. The former provide their woven and nonwoven materials with labels which are to give the user information about sizes and instructions regarding cleaning, washing-temperatures and the like. The latter must provide their products with serial numbers and other variable relevant product information. Such users of labels, identification plates and the like, repeatedly demand the fulfillment of two conditions which the art has not to date been able to satisfy with available printing systems. The two conditions are permanency of print and the ability to rapidly alter variable data to be printed.
Depending upon the use, labels must be able to withstand relatively rough treatment processes, e.g., frequent washing and chemical agents. The same is true of identification plates which are cleaned by such agents. Nevertheless, it is expected that the respective information carriers will remain readable over long periods of time.
Another problem is the formation of variable data on the identification carriers. Identification plates, for example, carry regularly consecutive numbers, with the consequence that every identification plate is actually an original. Variable data also occur in the case of textile marking, for example, in the case of the specification of product batches or lots, and data about color and size.
It is clear that, in the mass production of identification plates and labels, what must be striven for is to produce rapidly and without problems, the selectively marked carrier.
In the case of the production of marked textile carriers with variable data, work is done today preponderantly with needle printers. They transfer the data delivered to them from a computer serially or line-by-line by needle pressure heads onto the substrate employing colored or carbon ribbons. They do not, however, produce a particularly clean impression and, above all, do not deliver an imprint which is satisfactorily resistant to washing and cleaning. The pigments available are comparatively easy to wash out or may fade, under certain circumstances. This method of printing is altogether unusable for the printing of textile labels of comparatively open weave, because the comparatively-liquid ink runs. In sum, the problem-free printing of variable data by this method of printing, where usable, is accompanied by deficient permanence of the impression. The opposite of this method is printing by hot-stamping, which delivers indicia to carriers that are resistant to washing and cleaning, and of outstanding quality, and for which shades and qualities of color are available in extraordinary abundance. But, in the case of this method of printing, the changing of data is time-consuming. In this operation the printed image is applied to the substrate which is to be printed, by means of a type block or stereotype plate. Where the data are variable, the blocks, or, respectively, the stereotype plates, must be changed every time the data are changed.
The present invention is directed to a method of printing, together with a printing system, which combines permanence with the ability to cheaply and automatically print variable data.